Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof;

FIG. 5 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing an alternative embodiment of our new design;

FIG. 6 is the second image thereof;

FIG. 7 is the third image thereof;

FIG. 8 is the fourth image thereof; and,

FIG. 9 is the fifth image thereof.

The appearance of the graphical user interface transitions sequentially between the images shown in FIGS. 1-4 in the first embodiment, and FIGS. 5-9 in the second embodiment. The process or period in which one image transitions to another forms no part of the claimed design. The broken lines showing a display screen or portion thereof and elements of the graphical user interface illustrate portions of the article, and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 